also: いっちょあがり
expression
order's up; coming up; one order ready
Used in food service or cooking contexts to announce that a dish or order is ready. Often said with a lively, informal tone.
「一丁上がり！」と料理人が威勢よく言った。
"Order's up!" the chef said energetically.
expression
problem solved; one down; all done
Extended use: said when a task or problem is finished, like 'that's one done' or 'all sorted'. Casual and often used in a self-congratulatory or relieved way.
やっとレポートが終わった。一丁上がり！
Finally finished the report. One down!
From 一丁 (one item/order) + 上がり (completion, from 上がる 'to finish'). Originally a cook's call, now used more broadly for completing any task.